Machine for cutting of masonry, wood and other materials

ABSTRACT

A machine for accurately cutting tiles, blocks of concrete, clay, blocks of stone and stone materials, wood and wooden materials is described. It may include a support stand which at its top supports a removable bed structure. The bed includes a motor-driven cutting disc recessed-mounted axially along pillow blocks such that a substantial portion of the cutting disc is projected above the bed surface and its mode of rotation is about a fixed centralized axis. Trolley track rails situated on distal ends of both long sides of the bed allow for lateral movement of the trolley above the bed surface to facilitate the cutting operation. During operation the object secured safely on the trolley which is manually moved towards the cutting disc while a perforated shower head sprays water onto the work piece. Water is filtered and recycled back to the shower via the bin situated below the cutting disc and then to the recycle and filter unit.

This application claims priority to provisional patent application No.61/582,072 filed Dec. 30, 2011, which is hereby incorporated herein byreference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates in general to machines used in theaccurate cutting of tiles of ceramic, porcelain, clay, marble, graniteand composites and similar, blocks of wood, quarry tiles, blocks ofconcrete or clay, blocks of stone, stone materials, slates,conglomerates and similar by the effective use of a sliding trolley on atrack or rails above a working table or bed secured upon a supportstructure. The movement of the trolley is to allow the work piece toengage the cutting tool or blade or disc where in this invention isfixed within the bed structure. It also relates to machines that can beeasily transported or moved given their compact and modularconstruction.

2. Related Art

Conventionally, methods used for the accurate cutting of tiles, concreteblocks, clay bricks, blocks of wood and blocks of stone have never beenconsolidated into a singular machine, but rather, each machine with aunique object of processing. The cutting of these objects is ordinarywithin the construction industry where it can be found the intricate useof tiles of porcelain, clay, ceramic, marble, slate and granite eachsometimes require unique and diverse cuts for specific sizing. Thesetiles are both functional and decorative in purpose where theirapplication can be found in interior and exterior floors, walls,columns, counters tops, showers and baths of domestic and commercialbuildings, roadways and walkways. Also, blocks of stone, concrete blocksand clay bricks are not all left without alteration requirements sinceproper building construction necessitates that these alterations be donesince they are the principal materials in use.

In many conventional designs there exists in general two methods ofengagement. First, a work piece is held fixed or fastened onto a bedsurface while a cutting tool attached to a moving arm (pivoted at oneend of the bed) is allowed to manually engage the work piece where allmeasures of control are exercised on the cutting tool. Or, second, acutting tool is held fixed either above in suspension to the bed surfaceor partially recessed in the bed surface and the work-piece is made tomanually engage the cutting tool either on a supported sliding table orunsupported, which by extension is of least accuracy.

BRIEF SUMMARY OF INVENTION

Accordingly, the limitations and problems as just described in the priorart are obviated according to the present invention as it relates inparticular to a machine so designed that a working platform or bed isremovably mounted onto a support stand or base with all degree ofmobility on natural and man-made surfaces. The bed is disposed over asemi-projected motor driven cutting disc such that an appropriateportion of the disc is available above the bed surface for the cuttingprocess. A trolley track allows manual movement of a trolley mounted onthe track to achieve a successful cut. The trolley through its designfacilitates the cutting process by securing the work piece using a blockguide and providing a through-pass for the cutting disc to engage thework piece on the trolley along the inscribed cut line while the trolleyis being moved in the direction of the cutting disc by means of asuitable handle. The rotation of the disc is typically in a directiontowards the bed center at the end where the object advances to thecutting disc so as to prevent ground particulates dispersion to the airfrom the cutting process.

In the non-wood cutting process, a shower sprays water onto the workpiece as a cutting aid and dust smother. Effluent water expended duringcutting is channelled through a bin and collected in a recycle andfilter unit where the water is filtered of entrained particulates bymeans of a series of filters and baffles and pumped back through theshower by means of a submersible pump, forming a closed-looped watercircuit. This system is meritorious, novel and eliminates dust and waterpollution associated with these processes since all is collected in therecycle and filter unit and the effluent water is not discharged intothe work environment.

The modular design of the recycle and filter unit is a practical featureof embodiments of the present invention, incorporating a shower, waterhoses and submersible water pump that collectively, can be utilized inconjunction with systems or machines requiring similar facilities duringmaterial cutting of similar type. A drain plug on one end of the unitcan be removed to drain the unit through an outlet port; this, togetherwith addition of fresh water, may keep the water turbidity withinacceptable measure. A means is available to admit water directly to theshower via a connected water valve without use of the recycle and filterunit as in situations where the submersible water pump were to fail inoperation due to electrical power failure or otherwise.

A bin positioned underside the bed serves as an intermediate accumulatorand channel for the guided passage of effluent water from the bedsurface and thence to the recycle and filter unit via a waste waterhose.

The bin as just mentioned is quite unique both in function and designand presents an advantageous effect in the operational features of thismachine. By virtue of its existence, there is no concern of waterflooding onto or around work areas, neither uncontrolled wood cuttingsnor sawdust left to the discretion of the wind, as the bin through itsplural functions eliminates these common problems. It must be emphasizedthat such features are incorporated with the consideration ofenvironmental preservation and cleanliness, which by extension makes fora comfortable work environment and increased worker safety. Suchfeatures are not likely seen in conventional machines.

The cutting of wood may be done in collaboration with a wood cuttingtable top locked onto the machine bed, where a blade slot ensures thecutting blade to be projected sufficiently above the wood cutting tabletop. A choice of wood cutting blade is discretionary owing to theinherent flexibility of operating modes. In such operation the wood isplaced onto the wood cutting table top, a transparent wood cuttingshield may be secured to the side of the machine bed and can be alignedand adjusted to provide suitable eye and operator protection. While theblade is in rotation, the wood piece is directed to the cutting blade ina manual fashion so as to cut the wood along inscribed cut lines in aneffective and safe manner. The pieces are removed and the process may berepeated. Wood shavings produced during wood cutting operation arecontained and directed where they can be easily disposed by disjoining alower section of the bin to efficiently remove the wood cuttings to anappropriate containment for disposal.

Various means is provided to dismount the machine into several modularunits comprising the wood cutting table top, trolley, wood cuttingshield, bed with motor and blade arrangement, recycle and filter unitand the bin, where each modular unit may be fitted with handles for easyremoval and mounting. The support stand may include both caster wheelsfor easy mobility and adjustable legs for stationary support.

BRIEF DESCRIPTION OF DRAWINGS

For a comprehensive exposure of the features, nature and advantageouseffects of the present invention, reference is now made to the detaileddescription in conjunction with the associated drawings, in which:

FIG. 1 is an isometric view of an exemplary apparatus in accordance withan embodiment of the present invention.

FIG. 2A is an isometric view of an exemplary apparatus including amounted trolley in accordance with an embodiment of the presentinvention.

FIG. 2B is another isometric view of an exemplary apparatus including amounted trolley in accordance with an embodiment of the presentinvention.

FIG. 2C is yet another view of an exemplary apparatus including a woodcutting table top and shield in accordance with an embodiment of thepresent invention.

FIG. 3 is an isometric view of an exemplary trolley apparatus inaccordance with an embodiment of the present invention.

FIG. 4 an assembly drawing of an exemplary shaft apparatus includingpillow block bearings, saucers, cutting disc and double pulleyarrangement in accordance with an embodiment of the present invention.

FIGS. 5A and 5B are isometric views of an exemplary bin apparatus andstrainer, respectively, in accordance with an embodiment of the presentinvention.

FIG. 6 is an isometric illustration of an exemplary recycling and filterunit (partially exploded) including hoses, pump, power supply and cover.

FIG. 7 is an isometric view of an exemplary wood cutting table top inaccordance with an embodiment of the present invention.

FIG. 8 is an illustration of a wood cutting shield assembly inaccordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates a block, stone, tile and wood cutting apparatus inaccordance with an exemplary embodiment of the present invention. Theapparatus comprises main support stand 1 which comprises adjustable legs6 appended at the base that provide stability and lockable wheels 15that provide means of mobility. Mountable upon support stand 1 isremovable bed 2 upon which certain modes of operation are carried out.Handles 13 may be fitted, preferably each short side, to facilitate easylifting and removing or mounting of bed 2 from or onto support stand 1.

Bed 2, much articulated by design, incorporates various features thatallow for attachment to other elements of the machine. In accordancewith a preferred embodiment and with reference to FIGS. 2A, 2B and 2C,frame motor support stand 21 is the attachment support for electricalmotor 11 that drives cutting disc 10 via a belt-pulley arrangement. Thisconfiguration can provide safety by virtue of its location under bed 2yet with an acceptable degree of accessibility to facilitate removal orservice. Bed support stand 14 may be provided to ensure the independenceof bed 2 when disjoined from the main support stand 1; as such, bed 2can remain unaided without care of obliqueness when placed on a naturalsurface. Frame motor stand support 21 may include belt guard supportbracket 20 that connects the belt guard 5 (see FIG. 1) in place so as toprovide a secure channel for belt movement throughout a straight pathwhere the belt (not shown) engages a double pulley 34 of cutting discassembly 68 (see FIG. 4). With reference to FIG. 4, cutting disc shaftassembly 68 may include double pulley 34 fixed onto a shaft 33 which maybe held in position by, e.g., pillow block bearings 35. Pillow blockbearings 35 may be supported by shaft support plate 19 (see FIG. 1) towhich the two pillow block bearings 35 are fastened. On an end of shaft33 distal to bed's 2 interior may be a terminal point of double pulley34 which is encompassed with the motor shaft (not shown) at the driverend via a drive belt (not shown). This configuration secures the passageand particularly isolates the belt from interference even by merit ofits short loop distance. On an end of shaft 33 proximal to bed 2interior is an access point where cutting disc 10 may be mounted ontoshaft 33; disc 10 may be held fast into position on the shaft betweentwo saucers 36. Returning to FIGS. 1 and 2A-C, access of cutting disc 10is provided above the surface of bed 2 by means of an adequately sizedopening 17 at an interior location of bed 2 thereby allowing the blade10 to be sufficiently projected above the surface of bed 2; thisprovides an adequate means for engagement of a work piece with blade 10during operation.

Bed 2 top surface may include a trolley track comprised of one or morerails 12; in a preferred embodiment, bed 2 includes two trolley trackrails 12 in close proximity to either long outer edge that traverseslinearly along the entire bed top surface. Trolley track rails 12 act asa conveyor for trolley 24 and a containment for water expended in thecutting process. Water expended during the cutting process may becontained by a circumscription formed by trolley track rails 12 on bothends and end stops 18 on the other two adjacent sides. The watercontained is not confined indefinitely, but may be discharged throughopening 17 into bin 3 of bin assembly 67 mounted at the underside. Inone embodiment, bin 3 may be supported beneath bed 2 by means of wingflanges 8 inserted through bed slots 71 and secured with pins 72.

With reference to FIGS. 2A, 2B and 3, in one exemplary mode ofoperation, trolley 24 is provided as a carriage operable to traverse bed2. End stops 18 may be provided on either or both extremes of bed 2.Trolley 24 is configured to support a work piece to safely engage thecutting tool or disc 10 and provides a means to achieve a most accuratecut once set. The movement of trolley 24 may be facilitated by wheels29, for example, four small sheaves or grooved-edged metal wheels fittedonto sides of trolley 24 and adequately spaced apart that trolley 24 mayroll on trolley tracks 12 on bed 2 unrestricted or without cause ofderailment. To promote this movement, handle 28 may be outfitted at anend of trolley 24 as a means of moving and controlling the trolley 24between both extremes of bed 2 in a very safe manner requiring no workercontact with the work piece.

In order for trolley 24 to slide over the projected cutting disc 10,access-way 30 is provided throughout the flat horizontal surface 26 oftrolley 24, essentially dividing the flat horizontal surface into twosections which are kept apart and fixed by two supporting end-faces 22.As such the access-way 30 is continued throughout these end faces 22just short of its length providing sufficient clearance for the cuttingdisc to pass uninhibited. The two end-faces 22 are held fast andsupported by means of a connecting arm 23 to the top of trolley 24. Aconcrete block guide 32 may be placed on one side of the trolley's flatsurface 26 and be used to keep the line of cut of the work-piece alignedto the cutting disc 10; this is accomplished by the concrete block guide32 acting as a backing edge that prevents lateral movement of thework-piece on trolley work surface 26. Easy adjusting and securing ofthe concrete block guide 32 may be provided by a fastening assembly. Inone embodiment, the fastening assembly may comprise two adjustment-nuts31 disposed to engage corner areas of concrete block guide 32. Withadjustment nuts 31 untightened, the concrete block guide 32 is free tomove laterally across the trolley work surface 26 to the point ofsupport to the work-piece. Concrete block guide 32 may then be securedin position by tightening both adjustment nuts 31. The means providedwithin trolley 24 to accommodate movement over the blade 10 iseffectuated during operation, as such; the operator may place thework-piece onto trolley work surface 26, fixed and aligned using theconcrete block guide 32. In operation trolley 24 is manually moved onrails 12 to the other end of the bed 2 surface while the cutting disc 10effectively passes through the access-way 30 of the trolley, engagingthe work-piece. When trolley 24 reaches the other end of bed 2, the cutwould have been concluded where the work piece can then be removed andtrolley 24 retracted to the start position. Trolley 24 design andfunction no longer require the hand of the operator to hold thework-piece to engage the cutting disc 10 as in many conventionalmachines. This minimizes the potential for unsafe conditions that canarise in operations of this nature.

In one embodiment, trolley 24 may comprise a water shower systemincluding shower 25 which may span trolley 24 above trolley work surface26. In accordance with this embodiment, the water shower may provide avery effective medium in the removal of grit produced during cuttingoperation and to aid as a lubricant to the cutting disc 10 in thecutting of materials other than wood. Shower 25 may comprise a pluralityof perforations in linear sequence and in such an arrangement to allowthe water to spray onto the entirety of trolley work surface 26. Thewater shower system may also include water valve 27. In one embodiment,water valve 27 may be disposed below handle 28 of trolley 24. Valve 27may be used to admit water through shower 25 or to isolate water fromshower 25 if water is not required. Water to shower 25 may be suppliedthrough nozzle 69 by hose 52 connected to submersible pump 46 locatedwithin recycling and filter unit 4 (see FIG. 6). Pump 46 may pump waterthrough supply water hose 52 which may be held stable by means of waterhose support 7 mounted onto a water hose support bracket at one side ofbed 2 frame. During operation, the silt contained within the effluentwater naturally flows through the access-way 30 on trolley 24 andthrough opening 17 in bed 2 and thus into bin assembly 67 where it ischannelled to recycling and filter unit 4 and can return to shower 25 asfiltered water. Non circulated water may be admitted directly to shower25 via connection of a water supply hose to nozzle 69, bypassing use ofthe recycle and filter unit 4 as in situations where submersible waterpump 46 fails in operation due to electrical power failure or otherwise.

With reference to FIGS. 5A and 5B, bin assembly 67 may be configured asan inverted pyramidal structure with a large open end connected underbed 2 surface in such a way as to follow-through from opening 17 in bed2; the other end of bin assembly 67 is ported by means of waste waternozzle 37 and connects to recycling and filter unit 4 via water nozzle37 and waste water hose 51 for transmission of waste water to same unitfrom bin assembly 67. In the illustrated embodiment, the shape of bin 3and bin assembly 67 may reduce the structural space required for themachine and can maintain the overall weight within acceptable limits. Inthe cutting of materials other than wood, a strainer 64, for example aperforated steel sheet with handle 42, may be inserted into bin assembly67 in a horizontal orientation in order to restrict any entrainedparticulates within the discharged water. The bottom of bin assembly 67,to which waste water nozzle 37 is attached, may be removed by detachingdetachable bottom-section 41. In one embodiment, detachablebottom-section 41 may be detachably attached by means of a tab, bolt andwing nut assembly (not shown) to the main part of the bin 3. As such, ina wood cutting mode of operation, strainer 64 may not be required andall wood shavings produced during operation are contained and directedin bin assembly 67 which are easily removed when bin assembly 67 isfilled by removing the bottom-section 41 and allowing the contents tofall into a disposable bag (not shown) or any similar disposal method ordevice. In addition, bin assembly 67 may be outfitted with one or morehandles, e.g., handle 38, for easy lifting and dismounting.

With reference to FIG. 6, recycling and filter unit 4 is so constructedto be modular in placement in relation to the machine. The said unit maybe of rectangular form and reside at the base of the support stand 1beneath bin assembly 67 where it can be easily removed by simply liftingand removing by the use of handle 43 on one end. Recycling and filterunit 4 may be closed by cover 65 with an appropriately sized inlet 48that ports waste water hose 51 from bin assembly 67; handle 49 may befitted at the top to accommodate removal of cover 65 and slot 47 may beextended from one end point of cover 65 to a suitable distance withincover 65 to permit the passage of supply water hose 52 and electricalpower cable (not shown) to water pump 46.

In one embodiment, recycling and filter unit 4 comprises a series ofchambers in sequential order with the first chamber being the largestand right-most according to FIG. 6. Cover 50 may be sealed onto the topchamber to create a partial enclosure. Baffle plates 45 may be used todivide the recycling and filter unit 4 into the various chambers

Effluent water leaving the bin assembly 67 enters the first chamber viawaste water hose 51. The water accumulation rate in the first chamber issufficient that through resident time, the larger of entrained sedimentsin the effluent water will settle at the bottom. On rising to the top ofthe chamber, water is filtered through an arrangement of perforations 73at the top of the baffle plate on one end. This filter process throughthe baffle restricts entrainments too large to pass through and causesthe water to accumulate within a second chamber which, being divided intwo, causes water flow to a sub-chamber by means of an opening throughthe bottom of the baffle plate creating said division. This sub-chamberfurther filters the water by means of an appropriate voluminous filtersuch as a sponge (not shown) that utilizes entirely the available space.Water is transmitted to a third chamber by means of an arrangement ofperforations 73 on the baffle plate on one end where it enters anothersub-chamber and thence to a main chamber by overflowing across a shortbaffle plate. The water flow from this third chamber to the other two isby similar overflow means into the last chamber where water pump 46 maybe disposed to circulate the filtered water.

Filtered waste water manifold 44 may be connected at the outside allchambers of the unit except the first; this manifold 44 allows recyclingand filter unit 4 to be easily cleaned out and all chambers drainedthrough said manifold 44 by removing an installed plug (not shown) atthe end.

Outlet port 16 may be connected to the inlet chamber at the end ofrecycle and filter unit 4 to facilitate draining the unit 4 of anyretained slush, sediments, water or to flush the unit 4 as required andto provide a means to relieve water from the unit 4 if there is norecycle water circuit due to an exclusion of water pump 46; in suchcase, it is adequate enough to admit non-circulated water through shower25, onto the work-piece, through the bin assembly 67, through the firstchamber of the recycle and filter unit 4 and thence through the outletport 16 as with a natural water flow.

With reference to FIGS. 2C and 7, in one embodiment, the cutting of woodmay be facilitated by the use of a wood cutting table top 63. Woodcutting table top 63 may be a flat rectangular table with handles 53located, e.g., centrally on both long sides, to provide lifting supportfor removal and mounting onto bed 2. Wood cutting table top 63 may beheld fast onto bed 2 by means of slotted plates 57, configured to engagewood cutting table top lock nuts 9, so as to lock the wood cutting tabletop 63 in place by tightening of wood table lock nuts 9. The position ofthe wood cutting table top 63, while mounted and held fast on the bed 2,provides access to wood cutting disc 10 sufficiently projected throughblade slot 70 to facilitate the appropriate cutting of wooden objects.Adjustable bar 58, of appropriate height and width and of a length thatspans the long side of the wood cutting table top 63 and in parallelrelation to the cutting disc 10, may be assembled onto the wood cuttingtable top 63 by means of supporting members that allow movement ofadjustable bar 58 across wood cutting table top 63 up to a point wherethe finest cut of a wooden object would allow. As such, adjustable bar58 serves as a guide and support in keeping a wooden object secured inposition so as to maintain the cutting mark on the work-piece in-linewith the cutting disc 10, i.e., the line of cut. The supporting memberswithin the constructs of the adjustable bar 58 may comprise nuts 54 thatdrive through adjustable stops 55 and into the end section of theadjustable bar 58. The movement of nut 54 screw-in-wise forcesadjustable stop 55 onto support 56 where by this action locks adjustablebar 58 in position; this construct may be on both end sides ofadjustable bar 58 and provides an effective means to allow easy mobilityand locking of adjustable bar 58. Supports 56 may be configured to fitbetween track rails 12 such that wood cutting table top 63 is supportedon bed 2 by track rails 12 and supports 56.

With reference to FIG. 8, in association with the wood cutting table top63 and the wood cutting process, wood cutting shield assembly 62 may beincorporated as an operator safety guard during the wood cuttingoperation. Wood cutting shield assembly 62 may comprise a transparentplastic sheet 66 (such as the brand PLEXIGLAS®) of a sufficient areadisposed in bracket 59 and connected to arm 60. The arm 60 may comprisehinge 61 at one end to optimize placement of sheet 66 about rotation Ain accordance with the operator's position. Exemplary alternatepositions are illustrated in dashed lines as sheet 66-R1 and 66-R2. Thisaction, with the combined effort of the horizontal, fully circularmovement provided by the arm 60 when inserted in shield assembly mountpivot 40 (see FIG. 2C) about rotation B, enables the wood cutting shieldassembly 62 to disposed in any position that may be required by theoperator. Wood cutting shield assembly 62 allows the operator to clearlyvisualise the cutting process with the adequate eye and face protectionthat is needed to ensure the safety of the operator. It provides goodimpact strength to withstand the impact of deflected projectilesdischarged during the wood cutting operation.

Adequate electrical power is supplied to an electric motor 11 to morethan sufficiently drive the cutting disc 10 via the belt and pulleyarrangement. An emergency stop button (not shown) is incorporated tosafely switch off the motor when not in use and an adequate over-currentprotection device (not shown) is connected to the electric motor mainsupply to ensure protection of the electric motor and other auxiliaries.Submersible water pump 46, housed within recycling and filter unit 4, ispowered from the electrical supply and is operated by means of a pumpswitch (not shown) independent of electric motor 11. A light may beinstalled (not shown) to give indication of the pump 46 status of ON orOFF as operated.

What is claimed is:
 1. A system for the cutting of constructionmaterials, said system comprising: a base configuration including astand, a bed removably mounted upon the stand and having an open portiontherein, a motor drivable blade-mounting shaft disposed beneath the bedand configured so that a circular blade mounted to the shaft isprojected through the open portion, and a bin disposed beneath the openportion; masonry cutting configuration components including a trackdisposed on the bed, a trolley configured to travel on the track, thetrolley having a work-piece placement surface with a blade channeltherethrough, and a masonry blade removably mountable to theblade-mounting shaft; and non-masonry cutting configuration componentsincluding a wood cutting table top removably mountable on the bed, and anon-masonry blade removably mountable to the blade-mounting shaft;wherein the system is configurable for alternate operations including; amasonry cutting operation in which the trolley is engaged on the track,the masonry blade is mounted on the blade-mounting shaft, and a masonrywork-piece may be disposed on the work-piece placement surface forcutting as the trolley traverses the track; and a non-masonry cuttingoperation in which the wood cutting table top is mounted on the bed, thenon-masonry blade is mounted on the blade-mounting shaft, and anon-masonry work-piece may be guided into the blade for cutting.
 2. Thesystem of claim 1 further comprising a filter and recycle unit in fluidcommunication with a drain of said bin, said filter and recycle unitconfigured to filter particulate matter from effluent detritus fromsawing operations.
 3. The system of claim 2 wherein: the trolley furtherincludes a shower configured to spray effluent on or about a work pieceduring sawing operations; the filter and recycle unit includes a pumpdisposed to pump filtered effluent to the shower; and the pump and theshower are connected in fluid communication.
 4. The system of claim 3wherein the filter and recycle unit comprises a sequence of a pluralityof chambers defined by baffles, said baffles and chambers configured toeffect settling and filtering of particulate matter from effluentdetritus.
 5. The system of claim 1 wherein the track comprises a pair ofrails and the trolley further includes wheels configured to engage therails.
 6. The system of claim 1, wherein the bin is a removable bin. 7.The system of claim 1, wherein the masonry cutting configurationcomponents further include a shower disposed on the trolley forshowering fluid on and about a work-piece.
 8. The system of claim 1,wherein the non-masonry cutting configuration components furtherincludes an adjustable guide bar mountable to the wood cutting tabletop.
 9. The system of claim 1, further comprising an articulabletransparent safety shield assembly, disposable between an operator ofthe system and the cutting operation.
 10. The system of claim 1, whereinthe masonry cutting configuration further includes a work-piece guidefastener.
 11. The system of claim 1 wherein the track is a pair ofrails.